Installations for the production of large quantities of oxygen and/or nitrogen by air distillation often comprise a spray refrigeration tower for cooling the compressed air so as to lower its temperature prior to its entry into adsorbent chambers for the removal of carbon dioxide and water, which are otherwise detrimental to the operation of the distillation cold box.
In the usual technique, all of the steam water (usually at saturation conditions) and carbon dioxide in the range of 270 to 350 ppmV are removed in a system of two or more adsorbent chambers loaded with special activated alumina and/or a molecular sieve. This technique has the drawback of necessitating large and expensive pressure vessels, costly adsorbents and high energy input for removing the carbon dioxide present in the air to the very low concentration levels required for the correct operation of the distillation cold box. Also, due to the general increase of carbon dioxide concentration in atmospheric air, especially in industrial areas, many existing installed units may face operation problems due to capacity limitations of their adsorbent chambers which may necessitate large revamping investments.
Certain techniques also exist for removing CO2 from a CO2 containing gas. For example, U.S. Pat. No. 6,524,843 (BLAIS et al.) discloses a bioreactor using immobilized carbonic anhydrase to capture CO2 from a gaseous effluent. This patent teaches that the bioreactor is a packed tower reactor to which a CO2-containing gas stream is fed. The solvent enters the packed tower and flows downwards while absorbing the dissolved CO2.
There is thus presently a need for a more efficient and less costly process and apparatus for the production of oxygen and/or nitrogen by air distillation.